This invention relates to a method and apparatus for locating an arc in a waveguide. Most prior art methods for locating an arc in a waveguide are inefficient or costly and tend to provide results which are only slightly better than mere guess work. The object of this invention is to provide a method and apparatus for locating waveguide arcs with good accuracy at a reasonable cost.
This invention takes advantage of the fact that when an arc occurs in a waveguide both vibratory and electromagnetic disturbances are produced. The disturbances can be detected by appropriate detectors. By measuring the time difference between the time of detection of the electromagnetic and vibratory disturbances, the location of the arc can be located with a high degree of accuracy. The electromagnetic disturbance is typically detected at a directional coupler which will measure a high voltage standing wave ratio (VSWR) in response thereto. This can often be done at no additional cost to the system employing the waveguide inasmuch as directional couplers are frequently used therewith, especially in high power radar applications. A sound transducer is acoustically coupled to the waveguide, preferably in the region of the directional coupler, for detecting the vibratory disturbance. The circuitry coupled to the detectors includes a counter and various timing circuits to measure the time interval between detections. The counter is preferably coupled to a display device via a display decoder and driver circuit. The timing circuits increment the counter at a rate which permits the number outputted from the counter to directly indicate the distance to the arc. Preferably, if the speed of the sound in the waveguide material is N units of distance per unit time then the counter is incremented at a rate of XN, where X is preferably an integer and more preferably a factor of ten. The number displayed at the display device will then be automatically calculated to the nearest 1/N units of distance. Of course, X may be a fractional quantity in some embodiments.
The advantages of the invention, both as to its construction and mode of operation, and the preferred mode of use, will be readily appreciated by those skilled in the art referring to the following detailed description of an illustrative embodiment when considered in conjunction with the accompanying drawings in which like reference numerals refer to the same component throughout the drawings.